Conventionally, there has been employed a vehicle brake apparatus for applying a braking force to a vehicle by pressing, by a motor, a brake pad mounted within a caliper against a disc rotor which is mounted to be rotatable in unison with a wheel. With this type of vehicle brake apparatus, in case the thickness of the disc rotor is not uniform along the peripheral direction of the disc rotor, there would occur a problem that the vehicle will be vibrated (abnormal vibration) due to variation that occurs in the braking torque in association with the disc rotor rotation when the brake pad is pressed against the disc rotor. As a technique to prevent occurrence of such abnormal vibration, there is a technique disclosed in a source identified below (e.g. Patent Document 1).
With an abnormal vibration preventing apparatus for an electric powered brake described in Patent Document 1, the apparatus includes an electric powered caliper drive device, a braking torque variation frequency detecting means for detecting a variable frequency of the braking torque or a caliper pressing force variation frequency detecting means for detecting a variation frequency of the caliper pressing force; and a speed variation frequency detecting means for detecting a wheel speed. According to this abnormal vibration preventing apparatus for an electric powered brake, if an output from the braking torque variation frequency detecting means or the output from the caliper pressing force variation frequency detecting means is greater than a reference value and this variation frequency is in proportion with the speed variation frequency, the electric powered caliper drive apparatus is controlled in inverted phase to the output variation. With this, the brake pad is controlled in its movement in such a manner as to cancel out the vibration, thus restricting the abnormal vibration.